Saturday, May 25, 2013

A paper published yesterday in Geophysical Research Letters finds, "The recent observed positive trends in total Antarctic sea ice extent are at odds with the expectation of melting sea ice in a warming world. More problematic yet, climate models indicate that sea ice should decrease around Antarctica in response to both increasing greenhouse gases and stratospheric ozone depletion." In fact, Antarctic sea ice has been at or near record high levels for the past several years. The authors conclude, "that it may prove difficult to attribute the observed trends in total Antarctic sea ice to anthropogenic [man-made] forcings."

Abstract: The recent observed positive trends in total Antarctic sea ice extent are at odds with the expectation of melting sea ice in a warming world. More problematic yet, climate models indicate that sea ice should decrease around Antarctica in response to both increasing greenhouse gases and stratospheric ozone depletion. The resolution of this puzzle, we suggest, may lie in the large natural variability of the coupled atmosphere–ocean-sea-ice system. Contrasting forced and control integrations from four state-of-the-art models, we show that the observed Antarctic sea ice trend falls well within the distribution of trends arising naturally in the system, and that the forced response in the models is small compared to the natural variability. From this, we conclude that it may prove difficult to attribute the observed trends in total Antarctic sea ice to anthropogenic forcings, although some regional features might be easier to explain.